This is backed by a regular heap allocation, so we can read and write to it.

Bug: b/139479506
Change-Id: I4a5ef04386120667a27c817c4ac0b59b8b44cd0b
Reviewed-on: https://swiftshader-review.googlesource.com/c/SwiftShader/+/35030Reviewed-by: Nicolas Capens <nicolascapens@google.com>
Tested-by: Ben Clayton <bclayton@google.com>
Kokoro-Presubmit: kokoro <noreply+kokoro@google.com>